Variation in the observed \(L_{\text{\,acc}}\)  is sometimes associated with the stellar rotation if the line of sight intercepts a single or multiple accretion spots [1]}, the properties of which are relatively stable over several rotation periods. For instance, [2]} show that the veiling measured in LkCa15 varies by a factor of \(\sim \!5\)  over the course of a few rotation cycles, and that this variability folds well in phase with the star’s rotation period (see their Fig. 5). Similarly, [3]} show that the veiling variability and, even more pronounced, the flux of the Hei emission line at 5876 Å of the star IP Tau have a clear modulation at the star’s rotation period.
